Elliptic Bus Bar Joining Structure for Laser Welding
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Solution Overview
Problem
In power supply devices requiring high voltage, the connection strength between bus bars and electrode terminals is compromised due to the need for insulation distance, leading to reduced welding strength when using resin walls and restricted jig sizes for pressing the bus bars.
Innovation Solution
The use of elliptically shaped joining portions and thin areas on the bus bars allows for secure pressing and welding, ensuring strong connections while maintaining a reduced bus bar size, with the bus bar partially having a thin area whose thickness is thinner than the other areas and an open window formed at the thin area, allowing for effective laser welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If walls made of insulating resin are provided between adjacent bus bars to secure insulation distance, then insulation performance is improved, but the size of the jig for pressing the bus bar is restricted, making it difficult to surely press the bus bar toward the electrode terminal
Solution Approach 1:
The patent changes the geometry of the joining portion from a conventional shape to an elliptic shape, utilizing the directional properties of the ellipse to create specific pressing surfaces. The elliptic joining portion has a long diameter direction and a short diameter direction, where the pressing surface is formed on the side surface in the short diameter direction. This dimensional transformation allows the jig to access and press the bus bar effectively even with insulating walls present between adjacent bus bars.
2Ease of operation
If the welding region is made small to secure space for the jig, then the jig can operate with restricted size, but the welding strength of the bus bar is reduced
Solution Approach 1:
The patent applies local quality by creating a thin area at the joining portion of the bus bar, where the thickness is reduced compared to other portions. This localized thinning concentrates the laser beam energy during welding, enabling strong welding connections in a compact region. The thin area serves as the specific welding region that provides both sufficient welding strength and adequate space for the jig to operate, resolving the contradiction between welding strength and jig operation space.
3Strength
If the bus bar is pressed toward the electrode terminal to ensure close contact, then connection strength is improved, but the required pressing force and jig complexity increase
Solution Approach 1:
The patent incorporates a pressing surface on the side surface of the elliptic joining portion in the short diameter direction, which is designed to receive pressing force from the jig. This preliminary preparation of the pressing surface geometry allows the bus bar to be easily pressed toward the electrode terminal with simpler jig design. The elliptic shape inherently provides the necessary contact geometry, reducing the complexity of the pressing mechanism while ensuring adequate connection strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures a strong and reliable connection between the bus bars and electrode terminals, enhancing the overall welding strength and allowing for a more compact bus bar design without compromising the connection integrity.
Implementation Method 1
by irradiating the laser beam at the boundary between the inserted electrode terminal and the bus bar, the electrode terminal and the bus bar are melted, connected at the boundary
Data Source
AI summary
A power supply device has; a battery stacked body where a plural sheets of battery cells each having a positive electrode terminal and a negative electrode terminal at one surface thereof are stacked; and a plurality of bus bars which connect the electrode terminals in the battery cells adjacently disposed. Each of the bus bars partially has a thin area whose thickness is thinner than a thickness of the other area, and an open window formed in the dun area, and opening a portion thereof. The thin area is formed in an oval shape elongated in the battery cell stacking direction, and the open window extends in a direction along the length of the oval shape. This configuration allows the thin area, above and below the length side of the oval shaped thin area, to be secured as a joining area for laser welding or the like.